Medium conveying device and image forming apparatus

ABSTRACT

The medium conveying device, comprises (1) a feeder configured to feed a print medium in a conveyance direction; (2) a stacker configured to stack the print medium fed by the feeder; (3) a first guide arranged in downstream side of the print medium in the conveyance direction, the first guide including a first guide surface configured to guide a downstream edge of the print medium stacked on the stacker; and (4) a second guide arranged to be movable with respect to the first guide, the second guide including a second guide surface configured to guide the downstream edge of the print medium stacked on the stacker, wherein the second guide configured to move with respect to the first guide such that the second guide surface protrudes with respect to the first guide surface in an upstream direction as the stacked amount of the print medium stacked on the stacker decreases.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119 to Japanese Patent Application No. 2017-189004 filed on Sep. 28, 2017, the entire contents which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a medium conveying device that conveys a print medium to an image forming apparatus such as a copier, a facsimile machine, and a printer.

BACKGROUND ART

Generally, an image forming apparatus such as a copier, a facsimile machine, and a printer can attach an external medium conveying device such that a print medium can be fed not only from inside of an apparatus but also from the outside of the apparatus. A conventional medium conveying device includes a feeding mechanism to feed the print medium. Further, a feeding mechanism feeds the print medium and conveys the print medium to a downstream side of a conveyance direction. For example, reference is made to U.S Pat. No. 7,850,163.

FIG. 12 is an operation explanatory diagram of a conventional medium conveying device. As illustrated in FIG. 12, the print medium M stacked on a stacker 1210 is fed one-by-one from bottom of the print medium.

However, in a configuration of the conventional medium conveying device, when a stacked amount of the print medium is small, the print medium cannot be fed and misfeeding can occur.

An aspect of the invention provides the medium conveying device in which it is possible to reduce an occurrence of misfeeding of the print medium even if the stacked amount of the print medium is small.

SUMMARY OF THE INVENTION

An exemplary medium conveying device is disclosed. The medium conveying device, comprises (1) a feeder configured to feed a print medium in a conveyance direction; (2) a stacker configured to stack the print medium fed by the feeder; (3) a first guide arranged in downstream side of the print medium in the conveyance direction, the first guide including a first guide surface configured to guide a downstream edge of the print medium stacked on the stacker; and (4) a second guide arranged to be movable with respect to the first guide, the second guide including a second guide surface configured to guide the downstream edge of the print medium stacked on the stacker, wherein the second guide configured to move with respect to the first guide such that the second guide surface protrudes with respect to the first guide surface in an upstream direction as the stacked amount of the print medium stacked on the stacker decreases.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic explanatory diagram illustrating a bottom sheet feeder and an image forming apparatus according to an embodiment.

FIG. 2 is an explanatory diagram illustrating a stacking and feeding mechanism in the bottom sheet feeder according to the embodiment.

FIG. 3 is an explanatory diagram illustrating an intra feeder conveying mechanism in the bottom sheet feeder according to the embodiment.

FIG. 4 is an explanatory diagram illustrating the image forming apparatus according to the embodiment.

FIG. 5 is a side view illustrating the main part periphery of the stacking and feeding mechanism in the bottom sheet feeder according to the embodiment

FIG. 6 is an external perspective view illustrating the main part periphery of the stacking and feeding mechanism in the bottom sheet feeder according to the embodiment.

FIG. 7 is an external perspective view illustrating a pressure guide in the bottom sheet feeder according to the embodiment.

FIG. 8 is a top view illustrating a feeder periphery in the bottom sheet feeder according to the embodiment.

FIG. 9 is a block diagram illustrating a control system in the bottom sheet feeder according to the embodiment.

FIG. 10 is an operation explanatory diagram illustrating the stacking and feeding mechanism when a stacked amount of a print medium is large in the bottom sheet feeder according to the embodiment.

FIG. 11 is an operation explanatory diagram illustrating the stacking and feeding mechanism when a stacked amount of a print medium is small in the bottom sheet feeder according to the embodiment.

FIG. 12 is an operation explanatory diagram of the conventional medium conveying device.

DESCRIPTION OF THE EMBODIMENT (1) First Embodiment

A first embodiment will be described in below. Common elements in each drawing are denoted with the same numerals. Hereinafter, a configuration of a medium conveying device and an image forming apparatus according to the first embodiment will be described. In the following description, a bottom sheet feeder 20 as the medium conveying device will be described as an example. In addition, although an envelope as a print medium will be described as an example, the print medium may be a commercially available cut paper, a transparent film paper, or the like.

FIG. 1 is a schematic explanatory diagram illustrating the bottom sheet feeder and the image forming apparatus according to the first embodiment. As illustrated in FIG. 1, the bottom sheet feeder 20 according to the first embodiment is detachably attachable to the image forming apparatus 10, and feeds the envelope M as the print medium to the image forming apparatus 10 as described later. The bottom sheet feeder 20 is inserted in an arrow X direction with respect to a tray opening 650 of a multi-purpose tray 600 (hereinafter, referred to as an “MPT”) in the image forming apparatus 10 and connected. The bottom sheet feeder 20 feeds from a bottommost envelope M of a plurality of stacked envelopes M with the envelopes M tilted in the conveyance direction and stacked. The bottom sheet feeder 20 includes a stacking and feeding mechanism 200 and an intra feeder conveying mechanism 250. The stacking and feeding mechanism 200 stacks the plurality of envelopes M and feeds the bottommost envelope M to the intra feeder conveying mechanism 250. The intra feeder conveying mechanism 250 further conveys the envelope M fed from the stacking and feeding mechanism 200 to the image forming apparatus 10.

The image forming apparatus 10 performs a desired print on the envelope M conveyed from the bottom sheet feeder 20 connected to the image forming apparatus 10. The image forming apparatus 10 includes an intra printer conveying mechanism 300, an image forming mechanism 400, an intermediate transferring mechanism 700, and a fixing and ejecting mechanism 800. The intra printer conveying mechanism 300 conveys the envelope M fed from the bottom sheet feeder 20 connected the image forming apparatus 10 to the inside of the image forming apparatus 10. The image forming mechanism 400 prints on the envelope M. More specifically, the image forming mechanism 400 forms an image. The intermediate transferring mechanism 700 intermediately transfers the image formed by the image forming mechanism 400 and transfers on the envelope M. The fixing and ejecting mechanism 800 fixes the image on the envelope M and ejects the envelope M.

Next, a configuration of the stacking and feeding mechanism 200 in the bottom sheet feeder 20 will be described in detail. FIG. 2 is an explanatory diagram illustrating the stacking and feeding mechanism in the bottom sheet feeder according to the first embodiment. As illustrated in FIG. 2, the stacking and feeding mechanism 200 stacks the envelopes M as the print medium with tilted in the conveyance direction and feeds from the bottommost envelope M. The stacking and feeding mechanism 200 includes a stacker 210, feeder 220, a gate part 230, and separator part 240. An arrow B indicates the conveyance direction conveyed the envelope M. Hereinafter, the arrow B is referred to as “conveyance direction”.

The stacker 210 stacks the envelope M as the print medium. The stacker 210 includes a stack guide 213 provided in a rear edge of the envelope M and a set guide 214 provided in left and right of the envelope M. The plurality of envelopes M stacked in stacker 210 may be same shape and size. The envelopes M are stacked in a state in which a front edge of the envelope M in conveyance direction is lower than a rear edge of the envelope M. More specifically, the envelopes M are stacked in a state tilted in the conveyance direction.

The envelopes M are regulated and aligned in the front direction in the drawing by the set guide 214 provided at both side surfaces of left and right of a device. More specifically, the envelopes M are regulated and aligned in a perpendicularly horizontal direction (hereinafter, a width direction) with respect to the conveyance direction of the envelopes M. The front edges of the envelopes M are contacted by a preliminary separating guide 231 of the gate part 230 and supported and stacked. In addition, the stack guide 213 is provided in the upstream side of the conveyance direction of the envelopes M, that is, the rear edge of the envelopes. Therefore, the stacker 210 stacks the envelopes M on a region in which the front-back and right-left is regulated by the stack guide 213, the set guide 214, and the preliminary separating guide 231 of the gate part 230.

The feeder 220 is arranged downward of near the downstream side of the conveyance direction in the stacker 210, that is, downward of near the front edges of the envelopes M. The feeder 220 feeds in order from the bottommost envelope M among the plurality of stacked envelopes M. The feeder 220 includes a feeding belt 221, a feeding drive roller 223 driving the feeding belt 221, a stretch roller 224, a pressure roller 228 and a paper end sensor 229. The feeding belt 221 is stretched between the feeding drive roller 223 and the stretch roller 224. Therefore, the feeding belt 221 contacts the bottommost envelope M among the plurality of stacked envelopes M on the stacker 210.

The feeding belt 221 is driven when a feeding and conveying drive motor 2102 illustrated in FIG. 9 is driven to rotate the feeding drive roller 223 in an arrow A direction. The paper end sensor 229 is provided between the feeding drive roller 223 and the stretch roller 224. The paper end sensor 229 detects that the envelopes M are stacked on the stacker 210. As described later, the feeding belt 221 is driven to rotate when the envelope M is detected by the paper end sensor 229. The pressure roller 228 is provided near the middle of the feeding drive roller 223 and the stretch roller 224, and presses the feeding belt 221 moving in the conveyance direction from downward to upward. Therefore, the feeding belt 221 forms a nip part between a pressing part 234-2 (see FIG. 7) at the lower of a guide surface 234-1 of the pressure guide 234 with pressing to upward by the pressure roller 228 and fees the bottommost envelope M on the stacker 210. The paper end sensor 229 may be a transmission type sensor, a reflection type sensor, or a mechanical sensor.

The gate part 230 separates the stacked envelopes M and is easy to feed the stacked envelopes M one-by-one. Especially, as a stacked amount of the envelopes M decreases, the gate part 230 is increased feeding force of the feeding belt 221 weakened by weight saving. The gate part 230 includes the preliminary separating guide 231 regulating the front edges of the envelopes M, the pressure guide 234 for increasing feeding force, a spring 238 as a urging member to pressure the pressure guide 234, and a reverse cam 239 as a swinging member for swinging the pressure guide 234.

The preliminary separating guide 231 contacts the front edges of the stacked envelopes M on the stacker 201 and separates the envelopes one by one before feeding the envelop M. The preliminary separating guide 231 is different in shape from an upper part and a lower part. The upper part of the preliminary separating guide 231 is provided vertically so as to line up the front edges of the conveyance direction of the envelopes M, or is provided to incline in downstream of conveyance direction. The lower part of preliminary separating guide 231 inclines such that the front edge of conveyance direction of the bottommost envelope M is slightly staggered forward from front edge of the envelope M right above. In other words, in an upper layer of envelopes M stacked on the stacker 210, the front edges of the envelopes are stacked on straight line. Meanwhile, a lower layer of the envelopes M stacked on the stacker 210 are stacked such that the front edge of conveyance direction of the bottommost envelope M is slightly staggered forward from front edge of the envelope M right above. Hence, the preliminary separating guide 231 can separate one by one before feeding the envelope M.

The pressure guide 234 according to the present embodiment includes an arm part 235 swinging around an arm fulcrum 235 a. The arm 235 is a part of the pressure guide 234. The pressure guide 234 includes the guide surface 234-1. The guide surface 234-1 is a surface of upstream side of the conveyance direction of the envelopes M, that is, the surface that contacts the stacked envelopes M. In addition, the preliminary separating guide 231 includes a guide surface 231-1 that contacts the stacked envelopes M. The guide surface 234-1 is provided on both sides in the width direction of the envelopes M of the guide surface 231-1. The guide surface 234-1 and the guide surface 231-1 are a surface of same height illustrated in FIG. 6, that is, a same surface. Since the guide surface 234-1 of the pressure guide 234 is fixed to the preliminary separating guide 231, the guide surface 234-1 of the pressure guide 234 does not rotate in the direction opposite to the arrow D direction (downstream of the conveyance direction) beyond the same surface of the guide surface 231-1 of the preliminary separating guide 231. Hence, when there is a large amount of the envelopes M, even if the pressure guide 234 is pressed by force (see Fp in FIG. 11) pressing the pressure guide 234 in downstream of the conveyance direction by the large amount of the envelopes M, the guide surface 234-1 of the pressure guide 234 the pressure guide 234 maintains same surface as the guide surface 231-1 of the preliminary separating guide 231.

Meanwhile, as the stacked amount of the envelopes M decreases, force Fp that presses the pressure guide 234 by the envelopes M weakens. As shown an arrow D, the pressure guide 234 inclines in upstream side of conveyance direction around the arm fulcrum 235 a by urging force of a spring 238. More specifically, left and right guide surface 234-1 of the pressure guide 234 gradually protrudes from the guide surface 231-1 of the preliminary separating guide 231. More specifically, the pressure guide 234 is supported to be able to incline to the feeding belt 221 and holds the envelopes M while contacting a front edges of the envelopes M. Further, as the stacked amount the envelope M decreases, the pressure guide 234 is inclined. Feeding force is increased by sandwiching the envelope M between the feeding belt 221 and the pressure guide 234.

The spring 238 as the urging member is provided so as to counter the force Fp that presses from a plurality of print media received by the pressure guide 234, the pressure guide 234 is urged and inclined toward upstream side of the conveyance direction as the stacked amount of the envelopes M decreases. One end of the spring 238 is fixed to a pressure guide frame 2007 fixed a device housing via a bridge 2005. For example, the spring 238 is included a coil spring or the like. The reverse cam 239 as the swinging member is driven to rotate a predetermined cycle in an arrow C direction by a drive unit 2103 illustrated in FIG. 9. The drive unit 2103 transmits a drive of the feeding and conveying drive motor 2102 via an electromagnetic clutch 2140 under the control of a controller 2100 and a motor controller 2101. The reverse cam 239 is contacted a cam working point of the arm part 235 of the pressure guide 234 by rotational drive of the reverse cam 239, and the arm part 235 is rotated in the opposite to arrow D direction. The pressure guide 234 is returned to an original position by rotating the arm part 235. If the reverse cam 239 is further rotated, the cam working point of the arm part 235 is out of contact, and the pressure guide 234 inclines in an arrow D direction. The pressure guide 234 is swung by repeating this.

More specifically, the reverse cam 239 is swung the pressure guide 234 to repeat contact and separation from the feeding belt 221 by inclining the pressure guide 234 at the predetermined cycle. The shape of the reverse cam 239 may be formed a shape with highest point per circumference of the reverse cam 230. As described later in FIG. 5, in downstream of the conveyance direction of the gate part 230, the separator part 240 is provided in upper part of the feeding belt 221. The separator part 240 includes the separator 2003 or the like for separating the envelopes M one-by-one when the plurality of envelopes is simultaneously fed.

Next, the configuration of the intra feeder conveying mechanism 250 in the bottom sheet feeder 20 will be described. FIG. 3 is an explanatory diagram illustrating the intra feeder conveying mechanism in the bottom sheet feeder according to the first embodiment. As illustrated in FIG. 3, the intra feeder conveying mechanism 250 of the bottom sheet feeder 20 is arranged in downstream of the conveyance direction of the feeder 220 in the stacking and feeding mechanism 200 and conveys the envelope M to the image forming apparatus 10. The intra feeder conveying mechanism 250 includes a conveying belt 251, a conveying table 253, a plurality of conveying rollers 254, a front edge sensor 255, and a second sensor 256. The conveying belt 251 sandwiches the envelope M between the plurality of conveying rollers 254, and conveys the envelope M in an arrow B direction while sandwiching the envelope M. The conveying belt 251 is transmitted drive force to the conveying drive roller 252 by the feeding and conveying drive motor 2102 illustrated in FIG. 9, and is driven when the conveying drive roller 252 is driven to rotate to an arrow A direction.

The conveying table 253 is a table that supports the conveyed envelope M. The second sensor 256 and the front edge sensor 255 are sensors that detect a position of the envelope M, and are used to control a drive of the conveying belt 251 and the feeding belt 221 in the feeder 220. The second sensor 256 and the front edge sensor 255 may be a reflection type sensor, a transmission type sensor, or a mechanical sensor. The envelope M conveyed while sandwiching by the conveying belt 251 is fed and conveyed to an inside of the image forming apparatus 10 by a pickup roller 602 and a feeding roller 601 or the like of the tray opening 650 of the image forming apparatus 10.

Next, the configuration of the image forming apparatus 10 will be described. FIG. 4 is an explanatory diagram illustrating the image forming apparatus according to the first embodiment. As illustrated in FIG. 1, the image forming apparatus 10 includes the intra printer conveying mechanism 300, the image forming mechanism 400, the intermediate transferring mechanism 700, and the fixing and ejecting mechanism 800. The intra printer conveying mechanism 300 is included in the MPT 600 or the like. The MPT 600 may include the pickup roller 602, the feeding roller 601, a retard roller 603 or the like. The pickup roller 602 contacts the envelope M as the print medium and feeds the envelope M. The feeding roller 601 feeds the fed envelope M to an apparatus body of the image forming apparatus 10. A retard roller 603 is urged to contact the feeding roller 601 for separating the fed envelope M one by one.

The bottom sheet feeder 20 is inserted to the tray opening 650 of the MPT 600 so that the front edge of downstream side of the conveyance direction of the conveying belt 251 in the bottom sheet feeder 20 is contacted to the pickup roller 602. When the bottom sheet feeder 20 is not inserted, the MPT 600 functions as a device for feeding a paper stacked on a paper stacking plate 604. In the downstream side of the conveyance direction in the MPT 600, a pair of conveying rollers 304 regulating a skew of the envelope M and a pair of rollers 305 feeding the envelope M to the image forming unit 400 are arranged. In addition, in the near the pair of conveying rollers 304 and the pair of conveying rollers 305, a sheet sensor 303, a sheet sensor 320, and a sheet sensor 330 are arranged. The sheet sensor 303 detects a drive timing of the pair of conveying roller 304. The sheet sensor 320 and the sheet sensor 330 detect a write timing in the image forming unit 400. The pair of conveying roller 304 and the pair of conveying roller 305 are driven to rotate by the drive motor which is not illustrated based on a detection result of the sheet sensor 320 and the sheet sensor 330.

The image forming mechanism 400 forms each color image of a yellow, a magenta, a cyan, and a black. The image forming mechanism 400 includes four image forming unit 400Y, 400M, 440C, and 400K. The four image forming unit 400Y, 400M, 400C, and 400K are attached the upper part of the intermediate transferring mechanism 700. The inside configuration of the image forming unit in each color is common. In the image forming unit 400Y, 400M, 400C and 400K, photoconductor drums 401 as image carriers are rotatable arranged in an arrow direction. In periphery of photoconductor drums 401, a charging roller 402 charged by supplying electrically charge the surface of the photoconductor drum 401 and an exposure device 850 that selectively irradiates the light to the surface of the charged photoconductor drum 401 and forms an electrostatic latent image are arranged. Further, in periphery of photoconductor drums 401, the developing roller 404 that is adhered the toner as a developer on the surface of the photoconductor drum 401 formed the electrostatic latent images and generates a toner image is arranged. In addition, when the toner image on the photoconductor drums 401 is transferred, a drum cleaning part 405 that removes the toner remaining on the surface of the photoconductor drum is arranged. The image forming mechanism 400 includes four toner container 406Y, 406M, 406C and 406 K containing yellow, magenta, cyan and black toners. The four toner container 406Y, 406M, 406C and 406 K contains the toner and supplies the toner to the developing roller 404.

The intermediate transferring mechanism 700 transfers the toner image formed by the image forming unit 400 to an intermediate transferring belt 701. Further, the toner image is transferred to the envelope M conveyed from the MPT 600. The intermediate transferring mechanism 700 includes a driving roller 702 driven to rotate by drive unit and a tension roller 703 that imparts tension to the intermediate transferring belt 701 by an urging method of coil spring or the like. In addition, the intermediate transferring mechanism 700 includes a secondary backup roller 704 opposite a secondary transferring roller 707 and transfers the toner image to the envelope M, and the intermediate transferring belt 701 stretched around the driving roller 702, the tension roller 703, and the secondary transferring backup roller 704. The intermediate transferring mechanism 700 further includes a belt cleaning part 706 and a primary transferring roller 705. The belt cleaning part 706 removes a toner remaining on the intermediate transferring belt 701. The primary transferring roller 705 is opposed to a photoconductor drum 401 and applies a predetermined voltage for transferring on the intermediate transferring belt 701.

The fixing and ejecting mechanism 800 comprises a pair of rollers including an upper roller 801 and lower roller 802. The upper roller 801 incorporates a halogen lamp 803 a as a heat source, and a surface of the upper roller 801 is formed by elastic body. The lower roller 802 incorporates a halogen lamp 803 b as a heat source, and a surface of the lower roller 802 is formed by an elastic body. The fixing and ejecting mechanism 800 applies heat and pressure to the toner image on the envelope M to melt the toner image so as to fix the toner image on the envelope M. After that, the envelope M is conveyed by a pair of ejecting rollers 804 a, a pair of ejecting rollers 804 b, a pair of ejecting rollers 804 c and a pair of ejecting rollers 804 d, and is ejected to the stacker 805 as indicated by an arrow Z. When the envelope M is ejected to the stacker 810, the envelope M is ejected by a pair of ejecting rollers 804 e. An ejecting sensor 806 detects the drive timing of the pair of ejecting roller 804 a, the pair of ejecting roller 804 b, the pair of ejecting roller 804 c and the pair of ejecting roller 804 d or the drive timing of the pair of ejecting roller 804 e.

Next, the stacking and feeding mechanism 200 in the bottom sheet feeder 20 according to the first embodiment will be described in more detail. FIG. 5 is a side view illustrating the main part periphery of the stacking and feeding mechanism in the bottom sheet feeder according to the first embodiment. FIG. 6 is an external perspective view illustrating the main part periphery of the stacking and feeding mechanism in the bottom sheet feeder according to the first embodiment. FIG. 6 is an external perspective view seen from an arrow Y direction illustrated in FIG. 5. The A-part illustrated in FIG. 5 will be described later. The stacking and feeding mechanism 200 of the bottom sheet feeder 20 includes by the stacker 210, the feeder 220, the gate part 230 and the separator part 240. The bottom sheet feeder 20 includes the bridge 2005 functioning as a structure (that is, a beam). The bridge 2005 is provided as the beam in a width direction of the envelope M, and is fixed to a frame of both sides of the bottom sheet feeder 20.

The stacker 210 includes the set guide 214 for regulating the width direction of the stacked envelopes M. The set guide 214 is arranged movably in accordance with the length of the width direction of the stacked envelopes M. Further, in the rear edge side of the envelopes of the stacker 210, the stack guide 213 is provided for supporting the rear edges of the envelopes. The separator part 240 includes a separator frame 2002, a knob 2004, a cam 2027, an inner rail 2025, an outer rail 2024, and a separator frame 2006 in addition to the separator 2003. The separator frame 2002 is connected to the bridge 2005 in downstream side of the conveyance direction of the bridge 2005. The separator frame 2002 includes the outer rail 2024 fixed to the separator frame 2002 and the inner rail 2025 slidable while being guided by the outer rail 2024.

When the knob 2004 is rotated, the inner rail 2025 moves upward and downward along the outer rail 2024 by rotating the cam 2027 and changing a contacting position of the cam 2027. In the lower edge side of the inner rail 2025, the separator frame 2006 is attached. In the separator frame 2006, the separator 2003 is attached so as to face the feeding belt 221. From the aforementioned configuration, the separator frame 2006 is moved upward and downward by rotating the knob 2004, and the separator 2003 can be pressed against to the feeding belt 221 or separated from the feeding belt 221. More specifically, a gap between the separator 2003 and the feeding belt 221 can adjust by a rotation operation of the knob 2004.

When the plurality of envelopes M are fed by the feeding belt 221, the separator 2003 can be fed only the bottommost envelope M and prevent overlap-feed since the feeding of the envelope M of the upper side among the plurality of envelopes is delayed by the friction of the separator 2003. For example, the separator 2003 includes a high friction member with large friction coefficient such as rubber.

FIG. 7 is an external perspective view illustrating the pressure guide in the bottom sheet feeder according to the first embodiment. The pressure guide 234 includes a guide surface 234-1 that contacts the front edge of the stacked envelopes M on the stacker 210. The guide surface 234-1 is provided in left and right of width direction of the envelopes M. The guide surface 234-1 includes a guide surface upper edge 234-4. The upper part of the guide surface upper edge 234-4 is bended in the conveyance direction side and does not contact with the front edge of the stacked envelopes M (see FIG. 6). Further, the upper part of the guide surface upper edge 234-4 is formed to reach a spring receiving part 234-8 which contacts on one edge of the spring 238.

The pressure guide 234 is formed the pressing part 234-2 for contacting with the feeding belt 221 or separating with the feeding belt 221 in lower part of left and right guide surfaces 234-1. Further, left and right arm parts 235 are formed from the left and right pressing part 234-2 toward downstream side of the conveyance direction. The front edge of downstream side of conveyance direction of the left and right arm part 235 contact with the reverse cam 239 as the swinging member. The arm fulcrum 235 a is provided in the middle of the arm part 235, and the arm part 235 swing around the arm fulcrum 235 a. Meanwhile, the spring 238 is provided to face the spring receiving part 234-8. The spring 238 is inclined the pressure guide 234 in the arrow D direction.

As a result, when the reverse cam 239 as the swinging member operates and the arm part 235 is moved in the arrow G direction, the pressure guide 234 is returned in the arrow H direction. Further, when the reverse cam 239 rotates and the arm part 235 is moved to the opposite side in the arrow G direction, the pressure guide 234 inclines in the arrow D direction. Hence, the pressure guide 234 always swing, and the pressing part 234-2 repeats contacting and separating with respect to the feeding belt 221.

Next, the configuration of the feeder 220 will be described. FIG. 8 is a top view illustrating the feeder periphery in the bottom sheet feeder according to the first embodiment. As illustrated in FIG. 8, the feeder 220 includes a feeding belt 221 a, a feeding belt 221 b, a feeding belt 221 c, a feeding belt 221 d, a feeding belt 221 e, a feeding belt 221 f, the feeding drive roller 223, the stretch roller 224, and the pressure roller 228. The feeder 220 feeds the envelope M in an arrow B direction by the feeding belt 221. The separator 2003 of the separator part 240 is arranged in the gap between the feeding belt 221 c and the feeding belt 221 d in the center among the plurality of feeding belt 221 provided in width direction. Even if the plurality of envelopes are fed at the same time, The feeding belt 221 a, the feeding belt 221 b, the feeding belt 221C, the feeding belt 221 d, the feeding belt 221 e, the feeding belt 221 f, and the separator 2003 separate and feed the envelopes M one-by-one.

Next, the configuration of the gate part 230 will be described. As illustrated in FIG. 5 and FIG. 6, the gate part 230 includes the preliminary separating guide 231, the pressure guide frame 2007, the pressure guide 234, the spring 238, and the reverse cam 239. The preliminary separating guide 231 is fixed to the bridge 2005. The pressure guide frame 2007 connected the bridge 2005 is provided a rotation fulcrum axis as the arm fulcrum 235 a. When the large amount of envelopes are stacked, the guide surface 234-1 of the pressure guide 234 is at the same height as the guide surface 231-1 of the preliminary separating guide 231. More specifically, the guide surface 234-1 of the pressure guide 234 and the guide surface 231-1 of the preliminary separating guide 231 are planar. In addition, a second gap 231-5 is formed to feed the envelope M between the feeding belt 221 and a lower part of the preliminary separating guide 231. Similarly, a first gap 234-5 is formed to feed the envelope M between the feeding belt 221 and a lower part of left and right pressing parts 234-2 of the pressure guide 234.

As illustrated in FIG. 6, left and right pressing parts 234-2 of the pressure guide 234 are positioned at the upper part of the feeding belt 221 c and the feeding belt 221 d. The pressure guide 234 may be provided at the upper part of feeding belt 221, the feeding belt 221 b, the feeding belt 221 e, or the feeding belt 221 f. The spring 238 is provided to incline the pressure guide 234 in an arrow D direction. The reverse cam 239 is driven to rotate in an arrow C direction by the drive unit 2103 illustrated in FIG. 9. The drive unit 2103 transmits driving force of the feeding and conveying drive motor 2102 via the electromagnetic clutch 2140 under a control of the controller 2100 and a motor controller 2101. The drive unit 2103 may be include a reverse cam drive motor as a drive motor different from the feeding and conveying drive motor 2102 to directly rotate the reverse cam 239 without the electromagnetic clutch 2140. The front edge of the arm part 235 of the pressure guide 234 is contacted with the reverse cam 239 by the rotation of the reverse cam 239. Hence, the pressure guide 234 is rotated in opposite to the arrow D direction (H direction as downstream side of the conveyance direction). and returned to the original position. The pressure guide 234 is swung by repeating this.

Next, the configuration of the control system of the bottom sheet feeder 20 according to the first embodiment will be described. FIG. 9 is a block diagram illustrating the control system in the bottom sheet feeder according to the first embodiment. As illustrated in FIG. 9, the control system of the bottom sheet feeder 20 includes the controller 2100. The paper end sensor 229, the front edge sensor 255, and the second sensor 256 as a sensor detecting the conveyance state of the envelope M are connected to the input side of the controller 2100. The motor controller 2101 driven to rotate the feeding and conveying drive motor 2102 is connected to output side of the controller 2100. From the aforementioned configuration, while the conveying state of the envelope M is detected by each sensor, the bottom sheet feeder 20 is rotationally driven the feeding drive roller 223 and the conveying drive roller 252 by the feeding and conveying drive motor 2102 under the control of the controller 2100 and the motor controller 2101. Further, while the conveying state of the envelope M is detected by each sensor, the reverse cam 239 is rotated by transmitting driving force of the feeding and conveying drive motor 2102 via the electromagnetic clutch 2140 under the control of the controller 2100 and the motor controller 2101, and the reverse cam 239 controls to repeat the swinging of the pressure guide 234.

From the aforementioned configuration, the bottom sheet feeder 20 and the image forming apparatus 10 according to the first embodiment operate as follows. First, the operation of the feeding and conveying of the envelope M in the bottom sheet feeder will be described by using in FIG.2 and FIG. 3. As illustrated in FIG. 2, the front edges of the stacked envelopes M on the stacker 210 are lower than the rear edges by the stack guide 213. The envelopes are stacked so that the load of the envelopes M applies the front edges of the envelopes. At this time, the envelopes M are regulated in the width direction of the envelopes M by left and right set guides 214. In addition, the preliminary separating guide 231 and the pressure guide 234 regulate the front edges of the envelopes. The preliminary separating guide 231 and the pressure guide 234 guide the envelopes M so that the envelopes of upper part does not proceed in downstream of the conveyance direction.

When the feeding belt 221 of the feeder 220 is driven, the stacked envelopes M are fed one-by-one from the bottommost envelope M in the conveyance direction (arrow B direction). The feeding belt 221 is driven by the feeding drive roller 223 driven to rotate by the feeding and conveying drive motor 2102 under the control of the motor controller 2101. The envelope M is fed to the second gap 231-5 provided between the preliminary separating guide 231 and the feeding belt 221. The envelope M of a amount regulated by the second gap 231-5 is fed in downstream of the conveyance direction. Hence, the regulated amount is not necessarily one.

The fed envelope M is fed to the nip part formed by the feeding belt 221 pressed by the pressure roller 228 and the pressing part 234-2 of the lower part of the pressure guide 234, and is conveyed to the separator 2003 of the separator part 240. When the plurality of envelopes M are conveyed at the same time, the plurality of envelopes M are separated one-by-one by the separator 2003. Further, the separated envelope M is conveyed to the intra feeder conveying mechanism 250 of downstream of the conveyance direction as illustrated the arrow B.

As illustrated in FIG. 3, the envelope M is further conveyed while sandwiching to downstream side of the conveyance direction by the nip part formed by the conveying roller 254 and the conveying belt 251 in the intra feeder conveying mechanism 250. The conveying belt 251 is driven by the conveying drive roller 252 driven to rotate by the feeding and conveying drive motor 2102 under the control of the motor controller 2101. The envelope M continues to convey to downstream side of the conveyance direction by the conveying belt 251, and is conveyed to the nip part formed by the pickup roller 602 provided the tray opening 650 of the image forming apparatus 10 and the conveying belt 251.

Next, the operation of the image forming apparatus 10 printing on the envelope M will be described by using in FIG. 4. When the image forming apparatus 10 receives a print instruction, the pickup roller 602 of the intra printer conveying mechanism 300 feeds the envelope M conveyed in the arrow B direction from the bottom sheet feeder 20 to downstream side of the conveyance direction. The fed envelope M is fed to the nip part formed by the feeding roller 601 and the retard roller 603 of the intra printer conveying mechanism 300, and is conveyed while sandwiching. At this time, in the parallel with an operation of feeding and conveying, the image forming mechanism 400 forms the toner image of the image instructed for printing by the image forming unit 400Y, the image forming unit 400M, the image forming unit 400C, and the image forming unit 400K.

The envelope M is further conveyed by a pair of conveying rollers 304 and a pair of conveying rollers 305 in the intra printer conveying mechanism 300. When the envelope M is conveyed to the intermediate transferring mechanism 700, the envelope M is conveyed while sandwiching by the nip part formed by an intermediate transferring belt 701 and a secondary transferring roller 707 in the intermediate transferring mechanism 700. At this time, the intermediate transferring belt 701 of the intermediate transferring belt 700 transfers the toner image formed by the image forming unit 400Y, the image forming unit 400M, the image forming unit 400C, and the image forming unit 400K the envelope M. Further, the envelope M continues to be conveyed to downstream of the conveyance direction and reaches to a position of the fixing and ejecting mechanism 800. Further, the envelope M is conveyed while sandwiching by the nip part 802 formed by an upper roller 801 and a lower roller 802 of the fixing and ejecting mechanism 800, and the fixing operation of the toner image is performed. The envelope M fixed the toner image is ejected to the stacker 805 by an ejecting roller 804 a, an ejecting roller 804 b, an ejecting roller 804 c, and an ejecting roller 804 d. Alternatively, the envelope M fixed the toner image is conveyed while sandwiching by the ejecting roller 805 a and an ejecting roller 804 e, and is ejected to a stacker 810.

Next, the control operation of the bottom sheet feeder 20 according to the first embodiment will be described by using in FIG. 9. The controller 2100 is driven to rotate the feeding and conveying drive motor 2102 by the motor controller 2101. More specifically, when the paper end sensor 229 of the feeder 220 detects that the envelope M is stacked on the stacker 210 and the front edge sensor 255 of the intra feeder conveying mechanism 250 or the second sensor 256 does not detects the envelope M, the controller 2100 is driven to rotate the feeding and conveying drive motor 2102. The feeding drive roller 223 of the feeder 220 and the conveying drive roller 252 of the intra feeder conveying mechanism 250 are driven to rotate by driving to rotate of the feeding and conveying drive motor 2102, and feeds and conveys the envelope M.

Meanwhile, when the paper end sensor 229 detects that the envelopes M are stacked and both of the front edge sensor 255 and the second sensor 256 detects the envelope M, the controller 2100 does not rotationally drive the feeding and conveying drive motor 2102. When the paper end sensor 229 does not detect that the envelopes M are stacked, the controller 2100 does not rotationally drive the feeding and conveying drive motor 2102 regardless of the detection result of the front edge sensor 255 and the second sensor 256.

When the stacked envelopes M on the stacker 210 is fed and conveyed by this control and the second sensor 256 detects the envelope M at first, the controller 2100 is driven to rotate the feeding and conveying drive motor 2102 so as to continue conveying of the envelope M by the motor controller 2101. After that, when the front edge sensor 255 detects the front edge of the envelope M, the feeding and conveying drive motor 2102 is stopped. At this time, the front edge of the conveyed envelope M positions in downstream sides of the conveyance direction than nip part formed by the pickup roller 602 and the conveying belt 251.

After that, the pickup roller 602 of the image forming apparatus 10 feeds the envelope M to downstream side of the conveyance direction by print operation of the image forming apparatus 10. Further, when the rear edge of the envelope M passes the second sensor 256, the controller 2100 is started rotation drive of the feeding and conveying drive motor 2102 by the motor controller 2101 and is conveyed the next envelope M to downstream side of the conveyance direction. The above detection timing changes by a length of the envelope M, a distance of the front edge sensor 255 and the second sensor 256, a printing speed of the image forming apparatus 10 or the like, but the feeding and conveying of the bottom sheet feeder 20 is controlled under the control of the controller 2100 and the motor controller 2101.

Next, the operation of the gate part 230 in the bottom sheet feeder 20 according the first embodiment will be described. FIG. 10 is an operation explanatory diagram illustrating the stacking and feeding mechanism when the stacked amount of a print medium is large in the bottom sheet feeder according to the embodiment. FIG. 11 is an operation explanatory diagram illustrating the stacking and feeding mechanism when the stacked amount of a print medium is small in the bottom sheet feeder according to the embodiment. FIG. 10 and FIG. 11 are a magnified view of A-part illustrated in FIG. 5.

As illustrated in FIG. 10, in a state in which the plurality of envelopes are stacked above the guide surface upper edge 234-4 of the pressure guide 234, the guide surface 234-1 of the pressure guide 234 is kept a pressed state toward the same surface side as the guide surface 231-1 of the preliminary separating guide 231. More specifically, a force Fp (part of gravity or load) that presses the pressure guide 234 toward downstream side of the conveyance direction by weight of the stacked envelopes M (gravity of load) is stronger than resultant force of a weight of the pressure guide 234 and the urging force Fs toward the upstream side of the conveyance direction by spring 238. As a result, the pressure guide 234 is held on the same surface as the preliminary separating guide 231 by fixing to the preliminary separating guide 231. The feeding force Fc is enough since total weight of stacked envelopes M in this case is large. Hence, misfeeding of the envelope M does not occur.

Meanwhile, as illustrated in FIG. 11, when the feeding of the envelope M progresses and the stacked envelopes M gradually decrease, the total weight of the stacked envelopes M becomes smaller and the feeding force Fc decreases. Further, when the stacked envelopes M gradually decrease, the force that presses the pressure guide 234 weakens by the weight of the stacked envelopes M. Further, when the resultant force of the weight of the pressure guide 234 and the urging force Fs of the spring 238 becomes stronger than the force Fp that presses the pressure guide 234, the pressure guide 234 inclines in the arrow D direction as upstream side of the conveyance direction around the arm fulcrum 235 a. More specifically, the guide surface 234-1 of the pressure guide 234 gradually protrudes from the guide surface 231-1 of the preliminary separating guide 231. As described above, when the staked amount of the stacked envelopes M on the stacker is smaller than a predetermined amount as compared with the case where the stacked amount of the stacked envelopes M on the stacker is larger than the predetermined amount, the guide surface 234-1 of the pressure guide 234 becomes a larger inclination amount than the guide surface 231-1 of the preliminary separating guide 231. Further, an inclination of the pressure guide 234 in the arrow D direction stops as the pressing part 234-2 of the lower edge of the guide surface 234-1 of the pressure guide 234 contacts the feeding belt 221. At this time, when the envelope M exists between the pressing part 234-2 of the pressure guide 234 and the feeding belt 221, the feeding force Fc increases and the envelope M is conveyed.

As described above, the feeding force Fc generated by the inclination of the pressure guide 234 is derived by the following equation 1. As illustrated in FIG. 11, the length from the arm fulcrum 235 a to center of gravity 234 g of the pressure guide 234 including the arm part 235 before inclination is L1, and the length from the arm fulcrum 235 a to a lower corner 234-2 of the pressure guide 234 is L2. The urging force which is a spring load of the spring 238 is Fs (gram), total weight of the stacked envelopes M is m (gram), the weight of the pressure guide 234 including the arm 235 is Ma (gram), and the coefficient of friction of the envelope M and the feeding belt 221 is μ. The feeding force Fc in this case is derived by the following equation.

The feeding force Fc=(m+Ma×L1/L2)+FS  (1)

Meanwhile, in the conventional the medium conveying device illustrated in FIG. 12, the feeding force Fc is the feeding force based only on total weight of the stacked envelopes M, the feeding force Fc=μm. Therefore, in the medium conveying device according to the first embodiment, the feeding force Fc can be increased by μ (Ma×L1/L2)+Fs. The urging force Fs of the spring 238 grasps the stacked amount of the envelopes M which misfeeding starts to occur in the conventional the medium conveying device, and may be de derived experimentally so that the pressure guide 234 inclines to the feeding belt 221 based on the stacked amount.

Hence, in the state which the pressing part 234-2 of the pressure guide 234 is kept in contact with the feeding belt 221, the remained envelope M may not be conveyed. The reverse cam 239 as the swinging member repeatedly performs the swinging motion of the pressure guide 234. More specifically, as illustrated in FIG. 11, the reverse cam 239 is rotated in the arrow C direction. The reverse cam 239 rotates by transmitting the driving force of the feeding and conveying drive motor 2102 via the electromagnetic clutch 2140 under the control of the controller 2100 and the motor controller 2101 illustrated in FIG. 9.

The arm part 235 contacting on the apex of the reverse cam 239 rotates in an arrow G direction as downstream side of the conveyance direction around the arm fulcrum 235 a by the rotation of the reverse cam 239, and the pressure guide 234 rotates in an arrow H direction. More specifically, the pressure guide 234 is a state illustrated in FIG. 10, the first gap 234-5 for feeding the envelope M is formed between the pressure guide 234 and the feeding belt 221. The bottommost envelope M can be fed to the first gap 234-5.

When the reverse cam 239 further rotates in C direction, the apex of the reverse cam 239 is in a state illustrated in FIG. 11 by releasing contact with the arm part 235. Hence, the arm part 235 rotates in opposite to the arrow G direction as upstream side of the conveyance direction by the urging force of the spring 238, and the pressure guide 234 inclines in arrow the D direction. More specifically, the pressure guide 234 is in the state illustrated in FIG. 11, the first gap 234-5 between the pressure guide 234 and the feeding belt 221 disappears. Hence, the pressing part 234-2 of the pressure guide 234 can be generated the feeding force with respect to the bottommost envelope M fed to the first gap 234-5.

In this way, the pressure guide 234 is swung in the arrow D direction and the arrow H direction by rotating the reverse cam 239. A rotation cycle of the reverse cam 239 as a predetermined cycle may be set so that the reverse cam 239 is rotated one or more times while being conveyed the envelope M with the shortest length in the conveyance direction. Hence, the pressure guide 234 swings one or more times. If the predetermined cycle is set as described above, even if the envelope M with the shortest length in the conveyance direction, the pressure guide is returned to the arrow H direction while being conveyed the previous one envelope M, and the front edge of the next envelope M passes the generated gap. Further, the front edge of the envelope M is sandwiched between the pressing part 234-2 of the pressure guide 234 and the feeding belt 221, the feeding force Fc increases, and the envelope M can be conveyed to the separator 2003.

As described above, according to the bottom sheet feeder of the first embodiment, in the bottom sheet feeder 20 feeding from the bottommost envelope M by the feeding belt 221, the pressure guide 234 is supported so as to be inclinable toward upstream side of the conveyance direction and holds the envelopes M by contacting the front edges of the stacked envelopes M. As the stacked amount of the envelopes M decreases, the pressure guide 234 is inclined and is increased feeding force by sandwiching the envelope M with the feeding belt 221. Hence, even if the stacked amount of the envelopes M is small, it is possible to feed and convey to the last envelope M without occurrence of misfeeding of the envelope M.

Further, the bottom sheet feeder 20 of the present embodiment is provided the reverse cam 239 for swinging the pressure guide 234 so as to repeatedly contact and separate between the pressure guide 234 and the feeding belt 221. Hence, when the pressure guide 234 is separated from the feeding belt 221, the envelope M can be fed between the pressure guide 234 and the feeding belt 221. In addition, when the pressure guide 234 contacts with the feeding belt 221, the feeding force can be increased since the envelope M is sandwiched.

In the description of the image forming apparatus 10 according to the first embodiment, the image forming apparatus 10 has been described as an electrophotographic image forming apparatus, but it may be the image forming apparatus such as an inkjet scheme or the like. In addition, in the description of the bottom sheet feeder 20 according to the first embodiment, the bottom sheet feeder 20 that includes the stacking and feeding mechanism 200 and the intra feeder conveying mechanism 250 has been described, but it may be omitted the intra feeder conveying mechanism 250.

Further, in the first embodiment, the bottom sheet feeder that feeds from the bottommost envelope M among the plurality of stacked envelopes M has been described, the invention is not limited to this. For example, it may be used for a method that feeds from the topmost envelope among the plurality of stacked envelopes M.

In the first embodiment, the feeding belt that feeds the envelope M has been described, the invention is not limited to this. For example, it may be used for a roller instead of the feeding belt.

The preliminary separating guide 231 corresponds to one specific example of “first guide” in the present invention. The guide surface 231-1 of the preliminary separating guide 231 corresponds to one specific example of “first guide surface”. The pressure guide 234 corresponds to one specific example of “second guide” in the present invention. The guide surface 234-1 of the pressure guide 234 corresponds to one specific example of “second guide surface” in the present invention. The arm fulcrum 235 a corresponds to one specific example of “rotation fulcrum” in the present invention. The feeding drive roller 223 corresponds to one specific example of “first roller” in the present invention. The stretch roller 224 corresponds to one specific example of “second roller” in the present invention. 

1. A medium conveying device comprising: a feeder configured to feed a print medium in a conveyance direction; a stacker configured to stack the print medium fed by the feeder; a first guide arranged in downstream side of the print medium in the conveyance direction, the first guide including a first guide surface configured to guide a downstream edge of the print medium stacked on the stacker; and a second guide arranged to be movable with respect to the first guide, the second guide including a second guide surface configured to guide the downstream edge of the print medium stacked on the stacker, wherein the second guide configured to move with respect to the first guide such that the second guide surface protrudes with respect to the first guide surface in an upstream direction as the stacked amount of the print medium stacked on the stacker decreases.
 2. The medium conveying device according to claim 1, wherein the first guide surface is arranged to incline with respect to the conveyance direction, the second guide moves with respect to the first guide such that the second guide surface inclines with respect to the first guide surface in the upstream direction as the stacked amount of the print medium stacked on the stacker decreases.
 3. The medium conveying device according to claim 1, further comprising an urging member that urges the second guide toward the direction projecting from the first guide surface.
 4. The medium conveying device according to claim 3, wherein the second guide further comprising: an arm part that extends toward downstream side of the conveyance direction from the second guide surface, and an arm fulcrum that is provided in the arm part, wherein when the stacked amount of the print medium stacked on the stacker becomes smaller than a predetermined amount, the second guide surface rotates toward the direction projecting from the first guide surface.
 5. The medium conveying device according to claim 1, further comprising a swinging member configured to swing the second guide with respect to the first guide, wherein the swinging member is driven to swing the second guide at least one or more times while the print medium is conveyed.
 6. The medium conveying device according to claim 1, wherein the feeder further comprising: a first roller that stretches a feeding belt and drives the feeding belt, and a second roller that stretches the feeding belt, wherein the feeder is arranged in vertically downward side of the stacker, wherein the feeding belt contacts a bottommost print medium among a plurality of print medium stacked on the stacker.
 7. The medium conveying device according to claim 6, wherein the second guide moves such that the second guide surface is closer to the feeding belt than the first guide surface.
 8. The medium conveying device according to claim 6, further comprising a swinging member configured to separate or contact the second guide with respect to the feeding belt, wherein the second guide is arranged so as to be contacted and separated with respect to the feeding belt.
 9. The medium conveying device according to claim 8, wherein the urging member is a cam, the second guide is separated from the feeding belt at a predetermined cycle.
 10. An image forming apparatus provided with the medium conveying device of claim 1, wherein the image forming apparatus performs a desired printing on the print medium conveyed from the medium conveying device. 